JPH0218168B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic plate thickness control device using different circumferential speed rolling for controlling plate thickness by adjusting the speed difference between the upper and lower rolling rolls in a rolling mill with separate drive of upper and lower rolls. It is.

Generally, in rolling mills such as plate mills and hot strip mills, the set value of the rolling mill roll opening is constant due to changes in the plastic deformation characteristics of the material and elastic deformation of the rolling mill, such as elongation. It is widely known that the thickness of the material at the exit from the rolling mill fluctuates. 1st
The figure is a graph showing the plastic deformation characteristics of the material and the elastic deformation characteristics of the rolling mill, where P ₁ and P ₂ are the material plasticity curves,
M ₁ and M ₂ are rolling mill elastic deformation curves.

The plastic deformation characteristics of the rolled material depend on the inlet side plate thickness H, outlet side plate thickness h, average deformation resistance k, material plate width W, etc.
It is expressed as a functional relationship between the rolling load F and those variables. (Equation (1)) F=f (H, h, k, W) ...(1) The plasticity curve in Figure 1 is a depiction of Equation (1), but the thickness at the entrance side at rolling point 1 is If _H1 is the plasticity curve and the rolling machine elastic curve are P1 _{, M1} , and the roll opening setting value is _S1 , then the rolling load is _F1 and the exit plate thickness is _h1 . (Operating point) At point 2 when rolling has progressed, the entry side plate thickness among the variables in equation (1) changes to H ₂ (t ₁ < t ₂ ), (H ₁ < H ₂ ), and other parameters change. If it is held constant, the plasticity curve changes to approximately P ₂ , and as a result, the rolling load increases to F ₂ (F ₁ <F ₂ ), and the exit plate thickness becomes h ₂ as the rolling mill elongates. (Operating point) If the plastic property changes of the material are left unattended in this way, a product with a constant thickness cannot be obtained, so a function to keep the exit side plate thickness constant is required by some means, but conventional plate thickness constant control (AGC) Automatic Gagc Control)
BISRA AGC is commonly used as
It was hot. BISRA AGC is a method of modifying the roll opening to counteract the elongation of the rolling mill due to changes in rolling load, and is based on the principle explained below.

That is, if the elastic properties of the rolling mill are approximated by a straight line and the slope (hereinafter referred to as Mill's constant) is M (Ton/mm), then the plate thickness h at the exit side of the rolling mill will be as follows from FIG.

h=S+F/M (2) However, h: Material plate thickness at the exit side of the rolling mill (mm) S: Roll opening setting value (mm) F: Rolling load (Ton) M: Mill constant (Ton/mm) (2 ) According to the equation, the variation in the thickness of the exit side plate is △h=△S+△F/M (3) Therefore, if the roll opening setting value is corrected using the following equation (4), the change in the thickness of the exit side plate can be made zero.

△S=-△F/M (4) Figure 2 is a block diagram of this conventional BISRA AGC. In the figure, 1 is the work roll of the rolling mill, 2 is the back-up roll, 3 is the reduction screw, and 4 is the rolling mill. Machine housing, 5, a reduction motor and its connection control device, 6 for adjusting the roll opening degree;
is a roll opening automatic positioning device (APC), 7 is a roll opening detector, 8 is a load cell (rolling load detector), 9 is a memory device, 10 is a calculation block for elongation of the rolling mill, 11 is a tuning rate, S is the material to be rolled.

Next, the operation will be explained. Material S is rolling mill 4
When the rolling load is bitten, the rolling load at that point is stored in the memory 9.
is stored in memory Fo and BISRA AGC is started.
In other words, the change in rolling load F as rolling progresses is a memorized value.
It is detected as a difference from Fo, the calculation of equation (4) is performed by the expansion calculation block 10, and the result is given to the APC device 6 as a command value.

As a result, the rolling mill roll opening degree is corrected to the operating point shown in FIG. The tuning rate 11 in the block of Figure 2 is a constant that determines how much the elongation of the rolling mill is modified, and is 0≦α≦1.
is set within the range. If α=1, the amount of elongation
It is a 100% correction, and if α = 0, AGC
will not work.

Since the conventional BISRA AGC is configured as described above, first of all, it has the disadvantage that the operation of the AGC promotes changes in the rolling load. Looking at Figure 1
The rolling load change when AGC does not operate is △F ₂ =
F ₂ −F ₁ , whereas when AGC is operated, the load change becomes △F ₃ =F ₃ −F ₁ , ｜△F ₂ ｜＜｜△F ₃ ｜
It is.

However, when the rolling load changes, the deflection of the rolling rolls changes, which changes the flatness of the product and deteriorates the product quality in the width direction. For this reason, with conventional equipment, BISRA AGC at the final stand is often not applicable for thin materials and wide materials in hot strip mills, and in thick plate mills.
In some cases, it was necessary to add a special pass under light pressure called a shape correction pass after the final pass using AGC.

The ratio of rolling load change (△F ₃ ) when BISRA AGC/tuning rate α=1 to rolling load change (△F ₂ ) when AGC is not operated is determined from Fig. 1 and is as follows.

△F ₃ / △F ₂ = M + Q / M (5) where M: Mill constant (Ton/mm) Q: Plasticity constant (Ton/mm) (Slope of plasticity curve near the operating point) Normal hot strip Taking the mill final stand as an example, for a material with a board width of 1500 mm and a product thickness of 1.6 mm, Q =
3000Ton/mm, M=about 600Ton/mm
The ratio of equation (5) is △F ₃ /△F ₂ = 6 times. Also, in the actual measurement data for the schedule, α = 1
The rolling load change when AGC was operated was about 300 tons at the skid mark area, and an ear wave was generated at that area.

Also, the second drawback is that BISRA AGC
As shown in the figure, mil (elastic) is used to calculate the amount of mil elongation.
It is necessary to have a constant M as a model, but since the mill constant M is a complex function of sheet width, roll diameter, rolling reaction force, etc., there is a limit to its estimation accuracy.
There were limits to the improvement of AGC accuracy.

This invention was made in order to eliminate the drawbacks of the conventional method as described above, and it is possible to perform highly accurate rolling control by manipulating the rolling load by giving a speed difference between the upper and lower work rolls during rolling. The purpose is to provide an automatic rolling control device.

First, it will be explained with reference to FIG. 3 that the rolling load can be controlled by giving a speed difference between the upper and lower work rolls during rolling.

FIG. 3 is a graph showing the relationship between the different circumferential speed ratio, the rolling load, and the advance rate, and shows that the rolling force can be manipulated by changing the different circumferential speed rate.

Here, the different circumferential speed ratio X is defined below by the high-speed side roll speed _VH and the low-speed side roll speed _VL .

X=V _H −V _L /V _H ...(6) When the different circumferential speed rate X changes, the plastic properties of the material change, so a new variable X is added to the functional relationship in equation (1).
is introduced, resulting in the following equation (7).

F=F(H, h, k, W,
h＋∂F／∂k・△k＋∂F／∂W・△W＋∂F／∂X・△X
...(8) From equation (2), if the roll opening degree S is fixed, △h=△F/M ...(9) Therefore, to make the plate thickness deviation △h zero, from equation (9), △
It is sufficient to set F=0, and for that purpose, from equation (8), △X=-1/∂F/∂X(∂F/∂H・
△H＋∂F／∂h・△h＋∂F／∂k・△k＋∂F／∂W・△
W)...(10) Since the inside of the box on the right side of equation (10) is the rolling force change due to the external expression, if this is △F _D , then △X=-1/∂F/∂X・△F _D ... 11) That is, by controlling the different circumferential speed rates using equation (11), the plate thickness deviation can be made zero.

An embodiment of the present invention shown in FIG. 4 will be described below. In FIG. 4, 41 is an upper and lower work roll, 42 is an upper and lower backup roll, 43 is an electric motor that drives the upper and lower rolls, 44 is a speed control device thereof, 45 is a load cell, 46 is a memory device, 47
48 is a gain adjustment block, 48 is a different circumferential speed distributor for upper and lower rolls, 49 and 50 are detectors, 51 is a timing calculator, 52 is an upper and lower roll speed detector, 53
54 is a rolling mill housing; 5 is a different circumferential speed rate calculator;
5 is an initial speed setting device for the upper and lower rolling rolls, and S is a material to be rolled.

Next, the operation will be explained. Material S is rolling mill 5
4, the upper and lower roll speeds are set to speeds V _pH and V _pL that give a predetermined initial different circumferential speed rate Xo.

Xo=V _pH −V _pL /V _pH ……(12) Detector 4 whose tip of material S is installed on the exit side of the rolling machine
9, the rolling load Fo at that time is stored in the memory 46. When there is a disturbance in the material, such as a change in the entrance side plate thickness, a load change ΔF=F−Fo is detected and applied to the gain adjustment block 47. The gain adjustment block 47 stores the value of (∂F/∂X) ^-1 determined by the rolling schedule and the different peripheral speed rate as a function of the different peripheral speed rate X. ) to find the optimal value, stratify it, and store it. Gain adjustment block 4
When the different circumferential speed rate correction amount ΔX is obtained as the output of step 7, the different circumferential speed distributor 48 determines the upper and lower roll speed correction amounts, and the upper and lower roll speed control device 44 determines,
Correct up/down roll speed. Different peripheral speed distributor 48
is a tandem rolling mill that performs calculations to change the peripheral speed rate while keeping the rolling mill exit speed of the material S at a predetermined value. This is particularly important in hot strip mills and the like. Rolling machine exit speed of material V _S
and each work roll speed V _H , V _L on the high speed side and low speed side
The relationship is V _S = (1 + f _H ) V _H = (1 + f _L ) V _L
...(13) In order for the material speed to remain unchanged, from equation (13) △f _H・V _Hp + (1+f _H )△V _H =0 ......(14) △f _L・V _Lp + (1+f _L ) △V _L = 0 ... (15) As can be seen from Figure 3, the advance rate changes depending on the different circumferential speed rate X, so finding the first order change is △f _H = ∂f _H /∂X・△X ... ( ₁₆ ) △f _L = ∂f _{L /} ∂X · △ You can modify the circumferential speed rate.

△V _H = -1/1 + f _H・∂f _H /∂X・V _Hp・△X ... (18) △V _L = -1/1+f _L・∂f _L /∂X・V _Lp・△X ... ...(19) However, {V _H , V _L : High speed, low speed side roll speed V _S : Output side material speed 1+f _H , 1+f _L : Output side material speed Advance ratio to roll ∂f _H /∂X, ∂f _L / ∂X: Change of each advance rate with respect to different circumferential speed rates} With the above configuration, when the rolling force F changes, the different circumferential speed rates X cancel out the rolling force change △F and approach zero.
is adjusted, the rolling force remains constant, and therefore the thickness of the exit side of the material S is controlled to be constant. This plate thickness control is completed when the tail end of the material S reaches the detector 50 placed just before the rolling mill.

In the above embodiments, the rolling load is used as the detection end for the thickness deviation on the exit side, but a thickness gauge may be provided on the exit side of the rolling mill as the detection end and its signal may be used, and the detection end is not a particular problem. Not be left behind.

Moreover, a small calculator, an analog operational amplifier, etc. can be used as a specific control device of the present invention, and the means thereof are not particularly problematic.

As described above, according to the present invention, changes in rolling load are kept to a minimum by adjusting different circumferential speeds, so there is no adverse effect on the shape of the product.
AGC can be performed, and since the control method is feedback control, there is no control residual (= plate thickness deviation) due to Mill constant estimation error, etc. in BISRA AGC, and the finished plate thickness, shape, etc. AGC can be highly effective in terms of Further, even if the different circumferential speed rates between the upper and lower rolling rolls are changed, the speed at which the material exits the rolling mill is kept constant. Therefore, this method
If AGC is applied, it will become possible to perform AGC at the final stand of hot strip mills, and in plate mills, improvements will be made in terms of both quality improvement and operational efficiency, such as eliminating the need for shape adjustment passes. It is effective because it can be done.

[Brief explanation of drawings]

Figure 1 is a graph showing the plastic deformation characteristics of the material and the elastic deformation characteristics of the rolling mill, and Figure 2 is the conventional BISRA.
A block diagram of AGC, FIG. 3 is a graph diagram showing an example of rolling load and advance ratio during rolling at different circumferential speeds, and FIG. 4 is a block diagram showing an embodiment of the present invention. In the figure, 41 is a work roll, 42 is a backup roll, 43 is an electric motor, 44 is a speed control device, 45 is a load cell, 46 is a memory device, 47 is a gain adjustment block, 48 is a different circumferential speed distributor, 4
9 and 50 are detectors, 51 is a timing calculator, 5
2 is a speed detector, 53 is a different peripheral speed calculator, and 55 is an initial speed setter.

Claims (1)

[Scope of Claims] 1. A first adjustment device that adjusts the speed difference between a pair of upper and lower rolls of a rolling mill, and a rolling material on the exit side of the rolling mill by detecting a change in the rolling load of the rolls. a detection device for detecting a plate thickness deviation, and controlling the first adjustment device according to a detection signal of the detection device to adjust the speed difference between the upper and lower rolling rolls, thereby controlling the plate thickness deviation. An automatic sheet thickness control device for reducing thickness, characterized by comprising a second adjusting device for adjusting the speed of the upper and lower rolling rolls so as to keep the speed of the material to be rolled on the outlet side of the rolling mill constant. Plate pressure control device.